This invention relates to a roll of the type which has a hollow shell with a cross piece extending through the shell with a spacing and pressure chambers formed by seals in the space between the shell and cross piece in general, and more particularly to an improved sealing arrangement in such a roll, to permit it act in two opposite directions.
A roll with a revolving hollow shell forming the working roll circumference, a stationary cross piece extending through the shell lengthwise with a spacing from the inside circumference of the hollow roll all around, with ends extending from the shell, the cross piece adapted for the application of external forces to ends protruding from the hollow shell, means forming longitudinal chambers in the space between the hollow shell and the cross piece, and means supplying a pressure fluid to one of the longitudinal chambers so that the hollow shell is braced via the pressure liquid, is known in the art. A roll of this type in which the longitudinal chambers comprises a sealing arrangement mounted to the cross piece including transverse end seals disposed at the mutually opposite ends of the longitudinal chambers along the cross piece and the hollow shell, and strip-shaped longitudinal seal extending along the cross piece and the hollow shell, on both sides of the action plane of the roll, each longitudinal seal having a longitudinal edge engaging a longitudinal undercut at the cross piece and resting with its other longitudinal edge against the inside circumference of the hollow shell and directed at an angle toward the pressurized longitudinal chamber is described in German Pat. No. 11 93 739. By means of the longitudinal seals, a first longitudinal chamber situated on the side of the roll gap and a second chamber situated away from the first chamber are divided off. In the first longitudinal chamber, the hydraulic pressure responsible for generating the line pressure acts in the roll gap. Leakage oil passes into the second longitudinal chamber and is conducted off from there. In general, however, this second longitudinal chamber is not completely without pressure, but is also filled with pressure liquid and has a certain pressure which counteracts the pressure in the first longitudinal chamber situated on the side of the roll gap. Only the excess pressure in the first longitudinal chamber is then effective.
In the design of the longitudinal seals just described, it is predetermined which of the two longitudinal chambers must be the one with the higher pressure. The longitudinal seal is formed by a sealing strip which extends from the undercut in the cross piece outwardly at an angle toward the inside circumference of the hollow roll and must be directed toward the longitudinal chamber with the higher pressure so that the pressure acts against the "underside" of the sealing strip and presses the sealing strip against the inside circumference of the hollow shell with a sealing pressure which is the higher, the higher the pressure in the first longitudinal chamber. Hereinafter, the chamber with the higher pressure will be called the "pressure-effective" longitudinal chamber.
An asymmetry of the seal design, therefore, exists with respect to the meridian plane of the roll perpendicular to the action plane, which made it necessary heretofore to turn the cross piece 180.degree. C. if such a roll is to act upwardly, for instance, instead of downwardly. Cases in which such changes in the direction of action occur can happen in rolling arrangements with more than two rolls. For instance, it can become necessary, depending on the desired treatment of a paper web, to direct the preponderant pressure of a roll of the type described above, against the upper roll of a calender instead of against the lower roll.
It is, thus, an object of the present invention to develop a roll of the type described above in such a manner that a change in the direction of action is possible without having to turn the cross piece around.